An Improved Method for Monitoring Subglacial Lake Activity in Antarctica From ICESat-2

Subglacial lakes are an important part of the Antarctic basal hydrological system, with many active subglacial lakes distributed in the steep topography of eastern Antarctica. When the ice surface has a slope, the horizontal geolocation error and elevation error of ICESat-2 altimetry data introduce additional uncertainty in estimating the ice surface elevation change, which will affect our ability to precisely monitor the activities of subglacial lakes. Therefore, based on the classical repeat-track analysis, we use weighted total least-squares (WTLS) adjustment to quantify the impact of horizontal geolocation and elevation errors on the fitted ice surface elevation. Through an iterative process, we derive precise time series of elevation changes to meet the need for monitoring subglacial lake hydrological activities. Using this improved method, we obtained the volume changes of the CookE2 subglacial lake in East Antarctica from March 2019 to March 2023. The results showed that Lake CookE2 was continuously recharged by subglacial water during this period, with an average equivalent recharge rate of 0.054 km3/yr. The water supply in the main lake accounted for about 68.5% of the total. The SW lobe, located away from the main basin, exhibited hydrological activity again after the drainage event and was reclassified into the active lake domain. The new lake area is ~118.73 km2. Compared to the traditional method, the improved approach reduces the variance of unit weight by ~0.044 m in the lake basin and by ~0.062 m on the steep southern basin margin. The precision of elevation change in rugged topography or steep slope areas has been significantly improved, aiding in precise monitoring of subglacial lake water volume changes and in determining their outlines.